1. Field of the Invention
The invention relates to an image processing method and apparatus, more particularly to an interlaced image processing method and apparatus.
2. Description of the Related Art
Referring to FIG. 1, to reduce data transmission bandwidth, in conventional broadcasting of television programs, a frame 11 is divided into a top field 13 and a bottom field 15 using an interlacing technique, and the top and bottom fields 13, 15 are subsequently transmitted. The frame 11 includes a plurality of rows of scan signals. Each row of scan signals includes a plurality of pixels. The top field 13 includes odd-numbered rows of scan signals in the frame 11, and the bottom field 15 includes even-numbered rows of scan signals in the frame 11.
A flat panel display displays images using progressive scan. Line doubling is usually employed to display interlaced top and bottom fields 13, 15 using progressive scan. However, the display position of the bottom field 15 is moved ½ line upward in case line doubling is employed.
When line doubling is used to display interlaced top and bottom fields 13, 15 of a frame 11 that has horizontal lines therein, undesired flicker of the horizontal lines is perceived. This is mainly due to non-alignment and varying widths of the horizontal lines. Such a phenomenon is particularly noticeable when continuously playing still images.
Referring to FIG. 2, since the top and bottom fields 13, 15 include different parts of the frame 11, to avoid overly large differences therebetween, a conventional de-interlacing approach employed in the prior art involves subjecting the top field 13 to interpolation so as to generate an interpolated bottom field 17 to be displayed in place of the top field 13. Theoretically, the interpolated bottom field 17 will be similar to the bottom field 15.
Referring to FIG. 2 and Table 1, a simple example is given herein for the purpose of illustration. The top field 13 includes eleven rows of scan signals 131˜141. The eleven rows of scan signals 131˜141 are first to eleventh scan signals 131˜141, respectively, and the pixel values thereof are 0, 100, 0, 100, 100, 0, 0, 100, 0, 100, and 0, respectively. The bottom field 15 includes eleven rows of scan signals 151˜161. The eleven rows of scan signals 151˜161 are first to eleventh scan signals 151˜161, respectively, and the pixel values thereof are 0, 100, 0, 100, 0, 0, 100, 0, 100, 100, and 0, respectively. 0 represents the background pixel value, whereas 100 represents the pixel value of a horizontal line.
The interpolated bottom field 17 is generated as a result of linear interpolation of the top field 13, and includes eleven rows of scan signals 171˜181. The eleven rows of scan signals 171˜181 are first to eleventh scan signals 171˜181, respectively, and the pixel values thereof are 50, 50, 50, 100, 50, 0, 50, 50, 50, 50, and 0, respectively.
The largest pixel value difference between the same row of scan signals in the top field 13 and the bottom field 15 is 100, and the largest pixel value difference between the same row of scan signals in the interpolated bottom field 17 and the bottom field 15 is 50. Since flicker is more evident with an increase in the pixel value difference, although the conventional interpolation approach can slightly reduce flicker, the extent of improvement is still unsatisfactory.
TABLE 1DifferenceDifferencebetweenbetween top &interpolatedScanTopInterpolatedBottombottombottom field &signalfieldbottom fieldfieldfieldsbottom fieldRow 10500050Row 210050100050Row 30500050Row 410010010000Row 510050010050Row 600000Row 705010010050Row 810050010050Row 905010010050Row 1010050100050Row 1100000